Purpose:
To assess the effect of reducing oxygen delivery to the ciliary body on aqueous production.
Methods:
This study used pentobarbital anesthetized rabbits (n=12, 2.25 ± 0.75 kg) in which the following variables were measured: mean arterial pressure (MAP), intraocular pressure (IOP), and orbital venous pressure (OVP) by direct cannulation, hemoglobin percent saturation (HbO2%, pulse oximeter), arterial partial pressure of oxygen (PO2a, intra–arterial fiber optic probe), ciliary blood flow (BFcil, laser Doppler flowmetry), and aqueous flow (Flow, fluorophotometry). Measurements were made for 60 min before and during systemic hypoxia induced by respiring the animals with a mixture of nitrogen and room air. Responses were evaluated by 2–tailed paired t tests.
Results:
Data are presented as mean ± SE.
Conclusions:
Previous studies show that aqueous production decreases when ciliary blood flow is reduced below a critical level. Because aqueous production is an active process utilizing aerobic metabolism, we hypothesize that the sensitivity of aqueous production to reduced ciliary blood flow is due to the concomitant decrease in oxygen delivery. In support of this hypothesis, aqueous production decreases when oxygen delivery is reduced by lowering the amount of oxygen in the arterial blood without changing ciliary blood flow.
Keywords: aqueous • blood supply • ciliary body